1. Field of the Invention
The present invention relates to color photographic elements and, particularly, to photographic elements for a color diffusion transfer process.
More particularly, it relates to color diffusion transfer photographic elements using a silver halide developing agent capable of cross-oxidizing DRR compounds (the term "DRR" as used hereinafter refers to "dye-releasing redox").
2. Description of the Prior Art
It has been known to use hydroquinones in color diffusion transfer photographic elements. For example, such descriptions thereof appear in U.S. Pat. Nos. 3,537,849, 3,253,915, 3,039,869, 3,192,044, and 3,411,904, etc. The photographic elements described therein are color diffusion transfer photographic elements using a dye developing agent as a dye image-forming material. In greater detail, they are color diffusion transfer photographic elements wherein the dye image-forming material in a reduced state (i.e., the dye developing agent itself) is diffusible in an alkaline medium, but is mordanted in the image-receiving component to form a color image and an oxidized dye developing agent which are non-diffusible. The function of the above-described hydroquinones in such photographic elements is to assist the development of silver halide by the dye developing agent.
On the other hand, in addition to the above-described color diffusion transfer photographic elements, color diffusion transfer photographic elements are also known using as a dye image-forming material a DRR compound capable of releasing a diffusible dye as a result of a redox reaction with an oxidation product of a developing agent caused by development of silver halide. It has been described, for example, in Research Disclosure, No. 15162, page 79 (published in November, 1976) that, in such color diffusion transfer photographic elements, certain kinds of hydroquinones hinder cross-oxidation of the oxidation product of the developing agent and the DRR compound to control gradation.
In the present specification, a compound having the above-described function of controlling gradation is called a "competitive developing agent".
There is further description in Research Disclosure, No. 15162 that hydroquinone, methylhydroquinone and t-butylhydroquinone are particularly effective as the competitive developing agent. With hydroquinone, methylhydroquinone and t-butylhydroquinone, although an effect of controlling gradation is ascertained, as described therein, sufficient control of the gradation cannot be achieved.